Touch panel comprising conductive layers having opening overlapping with light-emitting element

ABSTRACT

To increase the detection sensitivity of a touch panel, provide a thin touch panel, provide a foldable touch panel, or provide a lightweight touch panel. A display element and a capacitor forming a touch sensor are provided between a pair of substrates. Preferably, a pair of conductive layers forming the capacitor each have an opening. The opening and the display element are provided to overlap each other. A light-blocking layer is provided between a substrate on the display surface side and the pair of conductive layers forming the capacitor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/725,205, filed May 29, 2015, now pending, which claims the benefit offoreign priority applications filed in Japan as Serial No. 2014-112316on May 30, 2014, Serial No. 2014-128409 on Jun. 23, 2014, and Serial No.2014-242912 on Dec. 1, 2014, all of which are incorporated by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

One embodiment of the present invention relates to a touch panel.

Note that one embodiment of the present invention is not limited to theabove technical field. One embodiment of the invention disclosed in thisspecification and the like relates to an object, a method, or amanufacturing method. One embodiment of the present invention relates toa process, a machine, manufacture, or a composition of matter.Specifically, examples of the technical field of one embodiment of thepresent invention disclosed in this specification include asemiconductor device, a display device, a light-emitting device, a powerstorage device, a memory device, an electronic appliance, a lightingdevice, an input device, an input/output device, a method for drivingany of them, and a method for manufacturing any of them.

In this specification and the like, a semiconductor device generallymeans a device that can function by utilizing semiconductorcharacteristics. A semiconductor element such as a transistor, asemiconductor circuit, an arithmetic device, and a memory device areeach an embodiment of a semiconductor device. An imaging device, adisplay device, a liquid crystal display device, a light-emittingdevice, an electro-optical device, a power generation device (includinga thin film solar cell, an organic thin film solar cell, and the like),and an electronic appliance may each include a semiconductor device.

2. Description of the Related Art

Recent display devices are expected to be applied to a variety of usesand become diversified. For example, a smartphone and a tablet with atouch panel are being developed as portable information terminals.

Patent Document 1 discloses a flexible active matrix light-emittingdevice in which an organic EL element and a transistor serving as aswitching element are provided over a film substrate.

REFERENCE Patent Document

[Patent Document 1] Japanese Published Patent Application No.2003-174153

SUMMARY OF THE INVENTION

What is desirable is a touch panel in which a display panel is providedwith a function of inputting data with a finger, a stylus, or the liketouching a screen as a user interface.

Furthermore, it is demanded that an electronic appliance using a touchpanel is reduced in thickness and weight. Therefore, a touch panelitself is required to be reduced in thickness and weight.

For example, in a touch panel, a touch sensor can be provided on theviewer side (the display surface side) of a display panel.

In a touch panel where a capacitive touch sensor is provided so as tooverlap with the display surface side of a display panel, when thedistance between a pixel or a wiring of the display panel and anelectrode or a wiring of the touch sensor is reduced, the touch sensoris likely to be influenced by noise caused when the display panel isdriven, which results in a reduction of the detection sensitivity of thetouch panel in some cases.

One object of one embodiment of the present invention is to improvedetection sensitivity of a touch panel. Another object is to provide athin touch panel. Another object is to provide a foldable touch panel.Another object is to provide a lightweight touch panel. Another objectis to provide a touch panel with high reliability.

Another object is to provide a novel input device. Another object is toprovide a novel input/output device.

Note that the descriptions of these objects do not disturb the existenceof other objects. In one embodiment of the present invention, there isno need to achieve all the objects. Other objects will be apparent fromand can be derived from the description of the specification, thedrawings, the claims, and the like.

One embodiment of the present invention is a touch panel including afirst substrate, a second substrate, a first conductive layer, a secondconductive layer, a first light-emitting element, a secondlight-emitting element, and a light-blocking layer. The first conductivelayer has a first opening, and the second conductive layer has a secondopening. The first conductive layer and the second conductive layer forma capacitor. The first opening and the first light-emitting elementoverlap with each other in a region. The second opening and the secondlight-emitting element overlap with each other in a region. The firstconductive layer and the light-blocking layer overlap with each other ina region. The second conductive layer and the light-blocking layeroverlap with each other in a region. The first light-emitting elementand the second light-emitting element are positioned between the firstsubstrate and the second substrate in a region. The first conductivelayer and the second conductive layer are positioned between the firstlight-emitting element or the second light-emitting element and thesecond substrate in a region. The light-blocking layer is positionedbetween the first conductive layer or the second conductive layer andthe second substrate in a region.

In the above embodiment, a CR value of the first conductive layer or thesecond conductive layer is preferably greater than 0 s and less than orequal to 1×10⁻⁴ s.

In the above embodiment, an aperture ratio of the first conductive layeror the second conductive layer is preferably greater than or equal to20% and less than 100% in a region.

In the above embodiment, it is preferable that the touch panel include athird conductive layer, the third conductive layer be provided closer tothe first substrate than the first conductive layer or the secondconductive layer, and a distance between the first conductive layer andthe third conductive layer or a distance between the second conductivelayer and the third conductive layer be greater than or equal to 25 nmand less than or equal to 50 μm in a region.

In the above embodiment, it is preferable that the touch panel include athird light-emitting element, the third light-emitting element ispositioned between the first substrate and the second substrate in aregion, and the third light-emitting element and the first openingoverlap with each other in a region.

In the above embodiment, it is preferable that the touch panel include afourth light-emitting element, the fourth light-emitting element ispositioned between the first substrate and the second substrate in aregion, and the fourth light-emitting element and the second openingoverlap with each other in a region.

In the above embodiment, it is preferable that the touch panel includean insulating layer, the first conductive layer and the secondconductive layer overlap with each other in a region, and the insulatinglayer is positioned between the first conductive layer and the secondconductive layer in a region.

In the above embodiment, it is preferable that the touch panel include afourth conductive layer, a fifth conductive layer, and an insulatinglayer. Here, the fourth conductive layer and the light-blocking layeroverlap with each other in a region, the fifth conductive layer and thelight-blocking layer overlap with each other in a region, the fifthconductive layer and the second conductive layer overlap with each otherin a region, the insulating layer is positioned between the firstconductive layer and the fifth conductive layer in a region, theinsulating layer is positioned between the second conductive layer andthe fifth conductive layer in a region, and the insulating layer ispositioned between the fourth conductive layer and the fifth conductivelayer in a region. The insulating layer has a third opening and a fourthopening. The first conductive layer and the fifth conductive layer areelectrically connected to each other through the third opening. It ispreferable that the fourth conductive layer and the fifth conductivelayer be electrically connected to each other through the fourthopening.

It is preferable that the touch panel further include a fifthlight-emitting element. At this time, it is preferable that the fourthconductive layer have a fifth opening, the fifth light-emitting elementis positioned between the first substrate and the second substrate in aregion, and the fifth opening and the fifth light-emitting elementoverlap with each other in a region.

One embodiment of the present invention can improve the detectionsensitivity of a touch panel. Alternatively, a thin touch panel can beprovided. Alternatively, a foldable touch panel can be provided.Alternatively, a lightweight touch panel can be provided. Alternatively,a touch panel with high reliability can be provided.

Alternatively, a novel input device can be provided. Alternatively, anovel input/output device can be provided. Note that the description ofthese effects does not disturb the existence of other effects. Oneembodiment of the present invention does not necessarily achieve all theeffects listed above. Other effects will be apparent from and can bederived from the description of the specification, the drawings, theclaims, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B show a structure example of a touch panel module of anembodiment.

FIGS. 2A to 2C show a structure example of a touch sensor of anembodiment.

FIGS. 3A to 3C show structure examples of a touch sensor of anembodiment.

FIGS. 4A and 4B show structure examples of a touch sensor of anembodiment.

FIGS. 5A and 5B show structure examples of a touch sensor of anembodiment.

FIG. 6 shows a structure example of a touch sensor of an embodiment.

FIGS. 7A to 7G show structure examples of a touch panel of anembodiment.

FIG. 8 shows a structure example of a touch panel of an embodiment.

FIGS. 9A to 9E show structure examples of a touch panel of anembodiment.

FIGS. 10A and 10B show a structure example of a touch panel of anembodiment.

FIGS. 11A and 11B show a structure example of a touch panel of anembodiment.

FIGS. 12A and 12B show a structure example of a touch panel of anembodiment.

FIG. 13 shows a structure example of a touch panel of an embodiment.

FIG. 14 shows a structure example of a touch panel of an embodiment.

FIG. 15 shows a structure example of a touch panel of an embodiment.

FIGS. 16A and 16B are a block diagram and a timing chart of a touchsensor of an embodiment.

FIG. 17 is a circuit diagram of a touch sensor of an embodiment.

FIGS. 18A to 18G each illustrate an electronic appliance of anembodiment.

FIGS. 19A to 19I illustrate electronic appliances of an embodiment.

FIG. 20 shows a structure of a touch panel of an example.

FIGS. 21A to 21C are photographs of a touch panel of an example.

FIG. 22 shows measurement results of parasitic capacitance and parasiticresistance of a touch panel of an example.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments will be described in detail with reference to drawings. Notethat the present invention is not limited to the description below, andit is easily understood by those skilled in the art that various changesand modifications can be made without departing from the spirit andscope of the present invention. Accordingly, the present inventionshould not be interpreted as being limited to the content of theembodiments below.

Note that in the structures of the invention described below, the sameportions or portions having similar functions are denoted by the samereference numerals in different drawings, and description of suchportions is not repeated. Further, the same hatching pattern is appliedto portions having similar functions, and the portions are notespecially denoted by reference numerals in some cases.

Note that in each drawing described in this specification, the size, thelayer thickness, or the region of each component is exaggerated forclarity in some cases. Therefore, embodiments of the present inventionare not limited to such a scale.

Note that in this specification and the like, ordinal numbers such as“first”, “second”, and the like are used in order to avoid confusionamong components and do not limit the number.

Note that the terms “film” and “layer” can be interchanged with eachother depending on the case or circumstances. For example, the term“conductive layer” can be changed into the term “conductive film” insome cases. Also, the term “insulating film” can be changed into theterm “insulating layer” in some cases.

Embodiment 1

In this embodiment, a structure example of a touch panel of oneembodiment of the present invention will be described with reference todrawings. In the description below, a capacitive touch sensor is used asa touch sensor of a touch panel.

Note that in this specification and the like, a touch panel has afunction of displaying or outputting an image or the like on or to adisplay surface and a function of a touch sensor capable of sensingcontact or proximity of an object such as a finger or a stylus on or tothe display surface. Therefore, the touch panel is an embodiment of aninput/output device.

In this specification and the like, a structure in which a connectorsuch as a flexible printed circuit (FPC) or a tape carrier package (TCP)is attached to a substrate of a touch panel, or a structure in which anintegrated circuit (IC) is directly mounted on a substrate by a chip onglass (COG) method is referred to as a touch panel module or simplyreferred to as a touch panel in some cases.

A capacitive touch sensor that can be used for one embodiment of thepresent invention includes a capacitor. The capacitor can have astructure in which a dielectric is provided between a first conductivelayer and a second conductive layer. At this time, part of the firstconductive layer and part of the second conductive layer each functionas an electrode of the capacitor. The other part of the first conductivelayer and the other part of the second conductive layer may eachfunction as a wiring.

Examples of the capacitive touch sensor are a surface capacitive touchsensor and a projected capacitive touch sensor. Examples of theprojected capacitive touch sensor are a self-capacitive touch sensor, amutual capacitive touch sensor, and the like, which differ mainly in thedriving method. The use of a mutual capacitive type is preferablebecause multiple points can be sensed simultaneously.

A touch panel of one embodiment of the present invention includes,between a pair of substrates, a display element and a capacitor includedin a touch sensor. Thus, a thin and lightweight touch panel can beobtained.

It is preferable that a pair of conductive layers included in thecapacitor each have an opening. It is preferable that the opening andthe display element overlap with each other. Such a structure enablesextraction of light emitted from the display element to the outsidethrough the opening, and therefore, the pair of conductive layersincluded in the capacitor do not necessarily have a light-transmittingproperty. That is, a material such as metal or alloy that has lowerresistance than a light-transmitting conductive material can be used asa material for the pair of conductive layers included in the capacitor.This reduces the influence of detection signal delay or the like andincreases the detection sensitivity of the touch panel. Furthermore,such a structure can be applied to large-sized display devices such astelevisions as well as portable devices.

Since the pair of conductive layers can be formed of a low-resistancematerial, each of the conductive layers can have an extremely small linewidth. That is, a surface area of each of the conductive layers whenseen from the display surface side (in a plan view) can be reduced. As aresult, the influence of noise caused by driving a pixel is suppressed,which increases detection sensitivity. Furthermore, even when thecapacitor included in the touch sensor and the display element includedin the pixel are provided close to each other and between the twosubstrates, a reduction in detection sensitivity can be suppressed.Thus, the thickness of the touch panel can be reduced. In particular, inthe case where a flexible material is used for the pair of substrates, aflexible touch panel that is thin and lightweight can be obtained.

In the case of using a projected capacitive type, the product ofresistance and capacitance (also referred to as a CR value or a timeconstant) of the first conductive layer is preferably as small aspossible. Similarly, the CR value of the second conductive layer ispreferably as small as possible.

For example, in the case of using a projected mutual capacitive type, apulse voltage is supplied to one of the conductive layers, and a currentflowing in the other conductive layer is sensed. At this time, as the CRvalue of the conductive layer where current sensing is performed issmaller, a change in current due to the presence or absence of a touchmotion can be increased more. Furthermore, as the CR value of theconductive layer supplied with the pulse voltage is smaller, delay inthe waveform of the pulse voltage is suppressed more and detectionsensitivity can be increased more.

In the case of using a projected self-capacitive type, a pulse voltageis applied to each of the pair of conductive layers, and a currentflowing in each of the conductive layers is sensed. Therefore, as the CRvalue of each of the conductive layers is smaller, detection sensitivitycan be increased more.

For example, the CR value of the first conductive layer or the secondconductive layer is greater than 0 s and less than or equal to 1×10⁻⁴ s,preferably greater than 0 s and less than or equal to 5×10⁻⁵ s, morepreferably greater than 0 s and less than or equal to 5×10⁻⁶ s, stillmore preferably greater than 0 s and less than or equal to 5×10⁻⁷ s,still more preferably greater than 0 s and less than or equal to 2×10⁻⁷s. In particular, when the CR value is 1×10⁻⁶ s or less, high detectionsensitivity can be achieved while the influence of noise is suppressed.

The first conductive layer or the second conductive layer preferably hasa mesh shape having a plurality of openings. At this time, the apertureratio of the first conductive layer or the second conductive layer (theproportion of the opening area of the first conductive layer or thesecond conductive layer per unit area) is preferably higher than atleast the aperture ratio of the pixel included in the touch panel. Whenthe aperture ratio of the first conductive layer or the secondconductive layer is higher than the aperture ratio of the pixel,blocking of light emitted from the pixel by the first conductive layeror the second conductive layer can be suppressed. When the apertureratio is increased by increasing the size of the opening, the area wherethe object overlaps with the first conductive layer or the secondconductive layer is reduced, and therefore, detection sensitivity isreduced in some cases. In view of this, the aperture ratio and anopening pattern are preferably set so that the opening area is smallerthan the area of the object.

For example, the aperture ratio of the first conductive layer or thesecond conductive layer is preferably higher than or equal to 20% andlower than 100%, more preferably higher than or equal to 30% and lowerthan 100%, still more preferably higher than or equal to 50% and lowerthan 100%.

The touch panel of one embodiment of the present invention has highdetection sensitivity and is less influenced by noise caused when adisplay panel is driven. Therefore, the thickness of the touch panelitself can be reduced. For example, the distance between the pair ofsubstrates included in the touch panel can be reduced to 50 nm or moreand 100 μm or less, preferably 200 nm or more and 50 μm or less, morepreferably 500 nm or more and 20 μm or less. When a flexible substrateis used for the pair of substrates at this time, a flexible touch panelstrong against bending can be obtained.

In particular, the distance between the first conductive layer or thesecond conductive layer and a conductive layer closer to the substrateprovided with the display element than the first conductive layer or thesecond conductive layer is set to, for example, greater than or equal to25 nm and less than or equal to 50 μm, preferably greater than or equalto 50 nm and less than or equal to 10 μm, more preferably greater thanor equal to 50 nm and less than or equal to 5 μm.

Furthermore, a light-blocking layer is preferably provided between thesubstrate on the display surface side and the pair of electrodesincluded in the capacitor. The light-blocking layer may have a functionof suppressing color mixing between adjacent pixels. When thelight-blocking layer is closer to the display surface than the pair ofelectrodes, reflection of external light by the pair of electrodes isprevented, and the pair of electrodes is prevented from being visuallyrecognized from the display surface side. Thus, the touch panel can havehigh display quality.

The light-blocking layer and the pair of electrodes included in thecapacitor are preferably provided between adjacent pixels when seen fromthe display surface side (in a plan view). Furthermore, the width ofeach of the pair of electrodes included in the capacitor is preferablysmaller than the width of the light-blocking layer or the intervalbetween the two adjacent pixels.

A more specific structure example of one embodiment of the presentinvention is described below with reference to drawings.

Structure Example

FIG. 1A is a schematic perspective view of a touch panel module 10 ofone embodiment of the present invention. FIG. 1B is a developed view ofthe schematic perspective view of the touch panel module 10. In thetouch panel module, a touch sensor module 20 and a display panel 30 areprovided to overlap with each other.

In the touch sensor module 20, a substrate 21 is provided with an FPC41. Furthermore, a touch sensor 22 is provided on a surface on thedisplay panel 30 side of the substrate 21. The touch sensor 22 includesa conductive layer 23, a conductive layer 24, and a conductive layer 25.Furthermore, the touch sensor module 20 includes a wiring 29 whichelectrically connects these conductive layers to the FPC 41. The FPC 41has a function of supplying a signal from the outside to the touchsensor 22. Furthermore, the FPC 41 has a function of outputting a signalfrom the touch sensor 22 to the outside. Note that the substrate withoutthe FPC 41 is also simply referred to as a touch sensor, or referred toas a touch sensor substrate or a touch sensor panel.

The touch sensor 22 includes a plurality of conductive layers 23, aplurality of conductive layers 24, and a plurality of conductive layers25. Each of the conductive layers 23 has a shape extending in onedirection. The plurality of conductive layers 23 are arranged in adirection crossing the extending direction. Each of the conductivelayers 24 is positioned between two adjacent conductive layers 23. Eachof the conductive layers 25 electrically connects two conductive layers24 adjacent in the direction crossing the extending direction of theconductive layers 23. That is, the plurality of conductive layers 24arranged in the direction crossing the extending direction of theconductive layers 23 are electrically connected to each other with theplurality of conductive layers 25.

Here, there is a region where the conductive layer 23 and the conductivelayer 25 overlap with each other. The conductive layer 23, theconductive layer 25, and an insulating layer which is providedtherebetween and functions as a dielectric form a capacitor 11.Therefore, the conductive layer 23 and the conductive layer 25 partlyfunction as the pair of electrodes of the capacitor 11.

Note that here, the plurality of conductive layers 24 are electricallyconnected to each other with the conductive layer 25. Alternatively, itis possible to employ a structure in which the conductive layer 24 has ashape extending in one direction like the conductive layer 23, aninsulating layer is provided between the conductive layer 23 and theconductive layer 24, and the conductive layer 25 is not provided. Inthis case, part of the conductive layer 24 functions as one electrode ofthe capacitor 11.

Note that, for example, a low-resistance material is preferably used asa material of conductive films such as the conductive layer 23, theconductive layer 24, and the conductive layer 25, i.e., a wiring and anelectrode in the touch panel. As an example, metal such as silver,copper, or aluminum may be used. Alternatively, a metal nanowireincluding a number of conductors with an extremely small width (forexample, a diameter of several nanometers) may be used. Examples of sucha metal nanowire include an Ag nanowire, a Cu nanowire, and an Alnanowire. In the case of using an Ag nanowire, light transmittance of89% or more and a sheet resistance of 40 ohm/square or more and 100ohm/square or less can be achieved. Note that because such a metalnanowire provides high transmittance, the metal nanowire may be used foran electrode of the display element, e.g., a pixel electrode or a commonelectrode.

In the display panel 30, a display portion 32 is provided over asubstrate 31. The display portion 32 includes a plurality of pixels 33arranged in a matrix. Each pixel 33 preferably includes a plurality ofsub-pixels. Each sub-pixel includes a display element. A circuit 34electrically connected to the pixel 33 in the display portion 32 ispreferably provided over the substrate 31. For example, a circuitfunctioning as a gate driver circuit can be used for the circuit 34. AnFPC 42 has a function of supplying a signal from the outside to at leastone of the display portion 32 and the circuit 34. An IC functioning as asource driver circuit is preferably mounted on the substrate 31 or theFPC 42. The IC can be mounted on the substrate 31 by a COG method or aCOF method. Alternatively, the FPC 42, a TAB, a TCP, or the like onwhich an IC is mounted can be attached to the substrate 31. Note that anobject in which an IC or a connector such as an FPC is mounted on thedisplay panel 30 can be referred to as a display panel module.

The touch panel module of one embodiment of the present invention canoutput positional information based on the change in capacitance by thetouch sensor 22 at the time of a touch motion. Furthermore, the displayportion 32 can display an image.

Structural Example of Touch Sensor

FIG. 2A is a schematic top view (schematic plan view) of part of thetouch sensor 22. FIG. 2B is an enlarged schematic top view of a regionsurrounded by dashed-dotted line in FIG. 2A.

As shown in FIGS. 2A and 2B, it is preferable that the conductive layer23 be partly narrowed so that the width of a portion crossing theconductive layer 25 is small. Thus, the capacitance of the capacitor 11can be reduced. In the case of using a self-capacitive touch sensor, thedetection sensitivity can be increased more as the capacitance of thecapacitor 11 is smaller.

Furthermore, it is preferable to provide, between the conductive layer23 and the conductive layer 24 which are adjacent to each other, aconductive layer 26 which is electrically insulated from theseconductive layers 23 and 24. The conductive layer 26 can suppress theformation of a thin portion of the touch sensor 22. For example, in thecase where the conductive layer 23 and the conductive layer 24 areformed over the same flat surface, the conductive layer 26 formed in amanner similar to that of the conductive layer 23 and the conductivelayer 24 can increase coverage of a thin film formed after the formationof these conductive layers; thus, a surface can be planarized.Furthermore, owing to the uniform thickness of the touch sensor 22,luminance unevenness of light emitted from the pixels through the touchsensor 22 can be reduced, so that the touch panel can achieve highdisplay quality.

FIG. 2C shows the case where the conductive layer 23 and the conductivelayer 24 are formed over different flat surfaces and the conductivelayer 25 is not provided. At this time, the conductive layer 26 may beformed over the flat surface over which the conductive layer 23 or theconductive layer 24 is formed, or may be formed over a flat surfacedifferent from the flat surface over which the conductive layer 23 orthe conductive layer 24 is formed. Note that the conductive layer 26 isnot necessarily provided if not necessary.

FIG. 3A shows an example of a circuit diagram of the touch sensor 22including a plurality of conductive layers 23 and a plurality ofconductive layers 24. In FIG. 3A, six conductive layers 23 and sixconductive layers 24 are shown for simplicity, but the number of theconductive layers 23 and the number of the conductive layers 24 are notlimited thereto.

One capacitor 11 is formed between one of the conductive layers 23 andone of the conductive layers 24. Therefore, capacitors 11 are arrangedin a matrix.

In the case of a projected self-capacitive type, a pulse voltage isapplied to each of the conductive layers 23 and 24 so that theconductive layers 23 and 24 are scanned, and the value of a currentflowing in the conductive layer 23 or the conductive layer 24 at thistime is sensed. The amount of current is changed when an objectapproaches, and therefore, positional information of the object can beobtained by sensing the difference between the values. In the case of aprojected mutual-capacitive type, a pulse voltage is applied to one ofthe conductive layers 23 and 24 so that one of the conductive layers 23and 24 is scanned, and a current flowing in the other is sensed toobtain positional information of the object.

The CR value of the conductive layer 23 or the conductive layer 24 isgreater than 0 s and less than or equal to 1×10⁻⁴ s, preferably greaterthan 0 s and less than or equal to 5×10⁻⁵ s, more preferably greaterthan 0 s and less than or equal to 5×10⁻⁶ s, still more preferablygreater than 0 s and less than or equal to 5×10⁻⁷ s, still morepreferably greater than 0 s and less than or equal to 2×10⁻⁷ s.

Each of the conductive layers 23 and 24 preferably has a lattice shapeor a mesh shape having a plurality of openings. FIG. 3B shows an exampleof a top surface shape of part of the conductive layer 23.

The conductive layer 23 shown in FIG. 3B has a lattice shape in which adistance P1 is provided in a lateral direction and a distance P2 isprovided in a longitudinal direction. The distance P1 and the distanceP2 are almost the same in FIG. 3B, but may be different from each other.For example, the distance P2 in a longitudinal direction may be largerthan the distance P1 in a lateral direction as shown in FIG. 3C, or thedistance P2 in a longitudinal direction may be smaller than the distanceP1 in a lateral direction. The same can be said for the conductive layer24.

The aperture ratio of the conductive layer 23 or the conductive layer 24(the proportion of the opening area in the conductive layer 23 or theconductive layer 24 per unit area) is preferably higher than or equal to20% and lower than 100%, more preferably higher than or equal to 30% andlower than 100%, still more preferably higher than or equal to 50% andlower than 100% in a region.

The aperture ratio can be easily calculated from the distance P1, thedistance P2, and the width of the conductive layer. Alternatively, whena region R is assumed to be a periodic unit in FIG. 3B, the apertureratio can be calculated from the ratio of the area of the region R tothe area of the conductive layer 23 included in the region R. Here, theregion R is a periodic unit of a periodic pattern of the conductivelayer 23. By arranging regions R longitudinally and laterally in aperiodic manner, the pattern of the conductive layer 23 can be formed.

In each of the conductive layer 23 and the conductive layer 24, the linewidth of a lattice is preferably greater than or equal to 50 nm and lessthan or equal to 100 μm, more preferably greater than or equal to 1 μmand less than or equal to 50 μm, still more preferably greater than orequal to 1 μm and less than or equal to 20 μm. The lattice having such anarrow line width allows adjacent pixels to be close to each other inthe case where the opening overlaps with the pixel as described later.Consequently, the touch panel can have higher resolution and higheraperture ratio.

FIG. 4A is an enlarged schematic top view of a region indicated by adashed-dotted line in FIG. 2B.

As shown in FIG. 4A, each of the conductive layers 23 and 24 preferablyhas a lattice shape (also referred to as a mesh shape). That is, each ofthe conductive layers 23 and 24 preferably has a plurality of openings(an opening 23 a and an opening 24 a). When the opening and the pixelare provided to overlap with each other as described later, lightemitted from the display element in the pixel is not blocked by theconductive layer 23 and the conductive layer 24, or a reduction in theluminance of light due to the transmission through the conductive layer23 and the conductive layer 24 does not occur. As a result, the touchsensor 22 can be used in the touch panel without a reduction in theaperture ratio of the pixel and the light extraction efficiency. It ispreferable that the conductive layer 25 similarly have a shape notoverlapping with the pixel.

In the structure shown in FIG. 4A, the conductive layer 24 and theconductive layer 25 are electrically connected to each other throughopenings 27 formed in an insulating layer positioned between theconductive layer 24 and the conductive layer 25. The capacitor 11 isformed in a portion where the conductive layer 23 and the conductivelayer 25 overlap with each other.

As shown in FIG. 4A, the shape of the conductive layer 25 crossing theconductive layer 23 preferably has two or more portions shaped likestrips whose long sides extend in a direction crossing the conductivelayer 23. The plurality of strip-like portions can reduce contactresistance between the conductive layer 24 and the conductive layer 25.Furthermore, electrical connection between the conductive layer 25 andthe conductive layer 24 can be kept even when part of the conductivelayer 25 is broken or a contact failure occurs in a portion where theconductive layer 25 and the conductive layer 24 are connected to eachother. Defects like the break and the contact failure might occurparticularly when the touch panel is used while being bent; therefore,the conductive layer 25 preferably has the above-described shape.

FIG. 4B shows an example of increasing the area where the conductivelayer 23 and the conductive layer 25 overlap with each other. In theexample, the conductive layer 25 overlaps with the conductive layer 23not only in the portion where the conductive layer 23 and the conductivelayer 25 cross each other but also in another portion, whereby thecapacitance of the capacitor 11 can be increased. The capacitance of thecapacitor 11 can be changed as appropriate by adjusting the area wherethe conductive layer 23 and the conductive layer 25 overlap with eachother or the dielectric constant or the thickness of the insulatinglayer, for example.

Furthermore, in the example shown in FIG. 4B, the conductive layer 26shown in FIGS. 2A to 2C is provided. As shown in FIG. 4B, a plurality ofisland-like patterns may be provided as the conductive layer 26.

FIG. 5A shows an example where the conductive layer 25 is not providedin the structure shown in FIG. 4A. In FIG. 5A, the conductive layer 23and the conductive layer 24 are provided to overlap with each other.FIG. 5B shows an example where the conductive layer 25 is not providedin the structure shown in FIG. 4B.

FIG. 6 shows an example of a boundary portion between the conductivelayer 23 and the conductive layer 24. As shown in FIG. 6 , an opening 22a surrounded by part of the conductive layer 23 and part of theconductive layer 24 may be formed in the boundary portion. Such astructure can significantly reduce the distance between the conductivelayer 23 and the conductive layer 24 and can increase mutual capacitancetherebetween. In particular, in the case of using a mutual capacitivetype, the distance between the two conductive layers is preferablyreduced to increase mutual capacitance.

Arrangement Example of Opening of Conductive Layer and Pixel

FIGS. 7A to 7G, FIG. 8 , and FIGS. 9A to 9E are schematic views eachshowing the positional relationship between a pixel, sub-pixels includedin the pixel, and the conductive layer 23 which are seen from thedisplay surface side. Note that although the conductive layer 23 isshown in FIGS. 7A to 7G, FIG. 8 , and FIGS. 9A to 9E as an example, thesame applies to the conductive layer 24 and the conductive layer 25.

In the example shown in FIG. 7A, the pixel 33 includes a sub-pixel 33R,a sub-pixel 33G, and a sub-pixel 33B. For example, the sub-pixel 33R,the sub-pixel 33G, and the sub-pixel 33B have a function of expressingred color, green color, and blue color, respectively. Note that thenumber and the colors of the sub-pixels included in the pixel 33 are notlimited thereto.

The sub-pixels included in the pixel 33 each have a display element.Typical examples of the display element include light-emitting elementssuch as organic EL elements; liquid crystal elements; display elements(electronic ink) that perform display by an electrophoretic method, anelectronic liquid powder (registered trademark) method, or the like;MEMS shutter display elements; and optical interference type MEMSdisplay elements. The sub-pixel may have a transistor, a capacitor, awiring that electrically connects the transistor and the capacitor, andthe like in addition to the display element.

Furthermore, this embodiment can be used in a transmissive liquidcrystal display, a transflective liquid crystal display, a reflectiveliquid crystal display, a direct-view liquid crystal display, or thelike. In the case of a transflective liquid crystal display or areflective liquid crystal display, some or all of pixel electrodesfunction as reflective electrodes. For example, some or all of pixelelectrodes are formed to contain aluminum, silver, or the like. In sucha case, a memory circuit such as an SRAM can be provided under thereflective electrodes, leading to lower power consumption. A structuresuitable for employed display elements can be selected from among avariety of structures of pixel circuits.

In the structure shown in FIG. 7A, one opening 23 a in the conductivelayer 23 is provided to overlap with three sub-pixels, i.e., thesub-pixel 33R, the sub-pixel 33G, and the sub-pixel 33B. In this manner,the opening 23 a in the conductive layer 23 is preferably provided tooverlap with one pixel 33. In other words, the pixels 33 and theopenings in the lattice of the conductive layer 23 are preferablyprovided at the same intervals. Such a structure allows the peripheralportions of the pixels 33 to have the same structures (e.g., thestructures of films in the pixels and in the periphery of the pixels,the thicknesses of the films, and the unevenness of surfaces thereof),leading to a reduction in display unevenness.

Note that two or more pixels 33 and one opening 23 a may overlap witheach other as shown in FIG. 8 , for example.

FIG. 7B shows an example where one opening 23 a and one sub-pixeloverlap with each other. When the conductive layer 23 is providedbetween two sub-pixels in one pixel 33 in a plan view, the wiringresistance of the conductive layer 23 can be reduced. Consequently, thedetection sensitivity of the touch panel can be increased.

FIG. 7C shows an example where the pixel 33 further includes a sub-pixel33Y in the structure shown in FIG. 7A. For example, a pixel capable ofexpressing yellow color can be used for the sub-pixel 33Y. Instead ofthe sub-pixel 33Y, a pixel capable of expressing white color may beused. When the pixel 33 includes sub-pixels of more than three colors,power consumption can be reduced.

FIG. 7D shows an example where one opening 23 a and one sub-pixeloverlap with each other, i.e., an example where the conductive layer 23is provided between two adjacent sub-pixels in a plan view. Note that astructure in which two of the four sub-pixels overlap with one opening23 a may be employed, although not shown.

In the examples shown in FIGS. 7A to 7D, sub-pixels of each color arearranged in a stripe pattern. Alternatively, as shown in FIGS. 7E to 7G,sub-pixels of two colors may be alternated in one direction, forexample. In a structure shown in FIG. 7E, the pixel 33 including foursub-pixels and one opening 23 a overlap with each other. In a structureshown in FIG. 7F, two adjacent sub-pixels and one opening 23 a overlapwith each other. In a structure shown in FIG. 7G, one sub-pixel and oneopening 23 a overlap with each other.

Furthermore, the sub-pixels included in the pixel 33 may differ in size(e.g., the area of a region contributing to display). For example, thesize of the sub-pixel of blue color with a relatively low luminosityfactor can be set large, whereas the size of the sub-pixel of green orred color with a relatively high luminosity factor can be set small.

FIGS. 9A and 9B each show an example where the size of the sub-pixel 33Bis larger than the size of the sub-pixel 33R and the size of thesub-pixel 33G. In the examples shown here, the sub-pixel 33R and thesub-pixel 33G are alternated. However, sub-pixels of each color may bearranged in a stripe pattern as shown in FIG. 7A and other drawings, andmay have different sizes from each other.

FIG. 9A shows a structure in which the pixel 33 including threesub-pixels and one opening 23 a overlap with each other. FIG. 9B shows astructure in which one opening 23 a and one sub-pixel 33B overlap witheach other and another opening 23 a and two sub-pixels (the sub-pixel33R and the sub-pixel 33G) overlap with each other.

Alternatively, pixel structures as those shown in FIGS. 9C to 9E can beemployed. Here, a column of the sub-pixels 33B arranged in a stripepattern is provided between columns in each of which sub-pixels 33R and33G are alternated. Furthermore, one sub-pixel 33B is provided betweenone sub-pixel 33R and one sub-pixel 33G.

In the structure shown in FIG. 9C, six sub-pixels (using two sub-pixelsfor each color) overlap with one opening 23 a. In a structure shown inFIG. 9D, three sub-pixels (using one sub-pixel for each color) overlapwith one opening 23 a. In a structure shown in FIG. 9E, one sub-pixeland one opening 23 a overlap with each other. Note that the pixelstructure is not limited to the structures described here, and astructure in which two or more adjacent sub-pixels and one opening 23 aoverlap with each other may be employed.

Note that although the positional relationship between the conductivelayer 23 and the sub-pixels is described here, the same applies to theconductive layer 24 and the conductive layer 25. That is, in the touchpanel of one embodiment of the present invention, the opening 23 a inthe conductive layer 23 overlaps with one or more sub-pixels in a regionand the opening 24 a in the conductive layer 24 overlaps with one ormore of the other sub-pixels in a region. Since each sub-pixel includesthe display element as described above, it can be said that the opening23 a and the opening 24 a each have a region overlapping with one ormore display elements.

Stacked-Layer Structure Included in Touch Panel

FIG. 10A is a schematic top view of part of the touch panel when seenfrom the display surface side. In FIG. 10A, the conductive layer 23, theconductive layers 24, the conductive layer 25, a light-blocking layer53, coloring layers 52R, 52G, and 52B, and the like are shown.

FIG. 10B is a developed schematic view of a stacked-layer structure ofFIG. 10A. As shown in FIG. 10B, the light-blocking layer 53, theconductive layer 23, the conductive layers 24, an insulating layer 28,the conductive layer 25, the coloring layers 52R, 52G, and 52B, anddisplay elements 51 are provided between the substrate 21 and thesubstrate 31.

Note that hereinafter, each of the coloring layers 52R, 52G, and 52B isalso simply referred to as a coloring layer 52 in the case of describingcommon points of the coloring layers 52R, 52G, and 52B withoutdistinguishing them.

Each coloring layer 52 has a function of transmitting light in aparticular wavelength range. Here, the coloring layer 52R transmits redlight, the coloring layer 52G transmits green light, and the coloringlayer 52B transmits blue light. One of the display elements 51 and oneof the coloring layers 52 are provided to overlap with each other,whereby only light in a particular wavelength range in light emittedfrom the display element can be transmitted to the substrate 21 side.

The light-blocking layer 53 has a function of blocking visible light.The light-blocking layer 53 is provided to overlap with a region betweentwo adjacent coloring layers 52. In the example shown in FIGS. 10A and10B, the light-blocking layer 53 has an opening provided to overlap withthe display element 51 and the coloring layer 52.

As shown in FIG. 10B, the light-blocking layer 53 is preferably providedcloser to the substrate 21 than the conductive layer 23, the conductivelayers 24, and the conductive layer 25. That is, the light-blockinglayer 53 is preferably provided closer to the display surface than theseconductive layers. Furthermore, the light-blocking layer 53, theconductive layer 23, the conductive layers 24, and the conductive layer25 preferably overlap with each other in a region. Such a structureallows the conductive layer 23, the conductive layers 24, and theconductive layer 25 to be less recognized visually by a user becausethese conductive layers are hidden by the light-blocking layer 53 whenseen from the display surface side. Such a structure is effectiveparticularly when the conductive layer 23, the conductive layers 24, andthe conductive layer 25 are formed using a material reflecting visiblelight such as metal or alloy.

In the structure shown in FIG. 10B, the conductive layer 23, theconductive layer 25, and the insulating layer 28 provided therebetweenform the capacitor 11. Furthermore, the two conductive layers 24 betweenwhich the conductive layer 23 is provided are electrically connected tothe conductive layer 25 through the openings 27 formed in the insulatinglayer 28.

Each of the conductive layer 23, the conductive layer 24, and theconductive layer 25 is preferably provided between two adjacent displayelements 51 in a plan view. Furthermore, each of the conductive layer23, the conductive layer 24, and the conductive layer 25 is preferablyprovided between two adjacent coloring layers 52 in a plan view. Notethat in the case where the area of the coloring layer 52 or the area ofthe display element 51 is larger than the opening area in thelight-blocking layer 53, part of the conductive layer 23, the conductivelayer 24, or the conductive layer 25 may overlap with the displayelement 51 or the coloring layer 52 in a region.

Note that in the example shown here, the coloring layer 52 is providedcloser to the substrate 31 than the conductive layer 23 or the like;however, the coloring layer 52 may be provided closer to the substrate21 than the conductive layer 23 or the like.

In the example shown in FIGS. 10A and 10B, the two conductive layers 24between which the conductive layer 23 is provided are electricallyconnected to each other with the conductive layer 25. However, theconductive layer 25 is not necessarily provided as described above.

FIGS. 11A and 11B show a structure example of the case where theconductive layer 25 and the opening 27 are not provided in FIGS. 10A and10B. As shown in FIG. 11B, the conductive layer 23, the conductive layer24, and the insulating layer 28 provided therebetween form the capacitor11.

The above is the description of the stacked-layer structure.

Cross-Sectional Structure Example

A cross-sectional structure example of the touch panel module 10 isdescribed below.

Cross-Sectional Structure Example 1

FIG. 12A is a schematic cross-sectional view of a touch panel module ofone embodiment of the present invention. In the touch panel module shownin FIG. 12A, a capacitor of a touch sensor and a display element areprovided between a pair of substrates, and therefore, the thickness ofthe touch panel module can be reduced.

The touch panel module has a structure in which the substrate 21 and thesubstrate 31 are bonded to each other with an adhesive layer 220. Theconductive layer 23, the conductive layer 24, the conductive layer 25,and the insulating layer 28 which form a touch sensor, a contact portion253, the coloring layer 52, the light-blocking layer 53, and the likeare provided on the substrate 31 side of the substrate 21. A transistor201, a transistor 202, a transistor 203, a light-emitting element 204, acontact portion 205, and the like are provided on the substrate 21 sideof the substrate 31.

An insulating layer 212, an insulating layer 213, an insulating layer214, an insulating layer 215, an insulating layer 216, an insulatinglayer 217, an insulating layer 218, a spacer 219, a conductive layer225, and the like are provided over the substrate 31 with an adhesivelayer 211 provided therebetween.

The light-emitting element 204 is provided over the insulating layer217. The light-emitting element 204 includes a first electrode 221, anEL layer 222, and a second electrode 223 (see FIG. 12B). An opticaladjustment layer 224 is provided between the first electrode 221 and theEL layer 222. The insulating layer 218 is provided to cover end portionsof the first electrode 221 and the optical adjustment layer 224.

In FIG. 12A, the transistor 201 for controlling current and thetransistor 202 for controlling switching are provided in the pixel 33.One of a source and a drain of the transistor 201 is electricallyconnected to the first electrode 221 through the conductive layer 225.

In FIG. 12A, the transistor 203 is provided in the circuit 34.

In the example illustrated in FIG. 12A, the transistors 201 and 203 eachhave a structure in which a semiconductor layer where a channel isformed is provided between two gate electrodes. Such transistors canhave a higher field-effect mobility and thus have higher on-statecurrent than other transistors. Consequently, a circuit capable ofhigh-speed operation can be obtained. Furthermore, the area occupied bya circuit portion can be reduced. The use of the transistor having highon-state current can reduce signal delay in wirings and can suppressdisplay unevenness even in a display panel or a touch panel in which thenumber of wirings is increased because of increase in size orresolution.

Note that the transistor included in the circuit 34 and the transistorincluded in the pixel 33 may have the same structure. Transistorsincluded in the circuit 34 may have the same structure or differentstructures. Transistors included in the pixel 33 may have the samestructure or different structures.

The light-emitting element 204 has a top-emission structure and emitslight to the second electrode 223 side. The transistors 201 and 202, acapacitor, a wiring, and the like are provided to overlap with thelight-emitting region of the light-emitting element 204. Thus, anaperture ratio of the pixel 33 can be increased.

The spacer 219 is provided over the insulating layer 218 and has afunction of adjusting the distance between the substrate 31 and thesubstrate 21. In FIG. 12A, the spacer 219 and an overcoat 267 of thesubstrate 21 are provided with a gap therebetween. Alternatively, asshown in FIG. 13 , components such as the overcoat 267 on the substrate21 side may be in contact with the second electrode 223 over the spacer219 in a region. Furthermore, as shown in FIG. 13 , the spacer 219 mayalso be provided outside the pixel 33, e.g., in a region overlappingwith the circuit 34 or in a peripheral portion of the substrate 21 orthe substrate 31. Although the spacer 219 is formed on the substrate 31side in the structure described here, the spacer 219 may be formed onthe substrate 21 side. For example, the spacer 219 may be provided on aninsulating layer 266, the overcoat 267, the coloring layer 52, or thelike.

As shown in FIG. 14 , a spherical spacer 226 may be used instead of thespacer 219. A light-transmitting material or a light-absorbing materialmay be used for the spherical spacer 226. Although a material such assilica can be used for the spacer 226, an elastic material such as anorganic resin or rubber is preferably used. In FIG. 14 , the spacer 226having elasticity is deformed and seems to be pressed from above andbelow.

An insulating layer 262, the light-blocking layer 53, an insulatinglayer 264, the conductive layer 23, the conductive layer 24, theinsulating layer 28, the conductive layer 25, the insulating layer 266,the coloring layer 52, and the like are provided on the substrate 31side of the substrate 21 with an adhesive layer 261 provided between thesubstrate 21 and them. Furthermore, the overcoat 267 covering thecoloring layer 52 may be provided.

The light-blocking layer 53 is provided closer to the substrate 31 thanthe insulating layer 262. The light-blocking layer 53 has the opening,and the opening is provided to overlap with the light-emitting region ofthe light-emitting element 204.

As examples of a material that can be used for the light-blocking layer53, carbon black, a metal oxide, and a composite oxide containing asolid solution of a plurality of metal oxides can be given. Stackedfilms containing the material of the coloring layer 52 are preferablyused for the light-blocking layer 53. For example, a material containingan acrylic resin can be used for each coloring layer, and astacked-layer structure of a film containing the material of thecoloring layer 52R transmitting red light and a film containing thematerial of the coloring layer 52B transmitting blue light can beemployed. Formation of the coloring layer 52 and the light-blockinglayer 53 using the same material can reduce a manufacturing cost becausethe same manufacturing apparatus can be used.

As examples of a material that can be used for the coloring layer 52, ametal material, a resin material, and a resin material containing apigment or dye can be given.

The insulating layer 264 is provided to cover the light-blocking layer53. The insulating layer 264 may have a function of a planarizationfilm. In the case where a material with low heat resistance is used forthe light-blocking layer 53, an organic insulating material ispreferably used for the insulating layer 264 because a layer with highplanarity can be formed at a low temperature. Alternatively, aninorganic insulating material is preferably used for the insulatinglayer 264 because the insulating layer 264 can function as an etchingstopper at the time of processing the conductive layer 23 and theconductive layer 24.

Each of the conductive layer 23 and the conductive layer 24 is providedto cover part of the insulating layer 264. Each of the conductive layer23 and the conductive layer 24 overlaps with the light-blocking layer 53in a region. In FIG. 12A, the example where the conductive layer 24 isprovided in part of a region of the pixel 33 is shown. The opening 24 ain the conductive layer 24 overlaps with the light-emitting element 204in a region. In the pixel 33, the conductive layer 24 is provided tosurround the light-emitting region of the light-emitting element 204.Therefore, the conductive layer 24 may overlap with, for example, thespacer 219, the insulating layer 218, the conductive layer 225, thetransistor 201, the transistor 202, or a wiring electrically connectedto the transistor 201 or 202 in a region. The same applies to theconductive layer 23 and the conductive layer 25.

In the example shown in FIG. 12A, the conductive layer 23 and theconductive layer 24 are processed using the same conductive film. Sincethe conductive layer 23 and the conductive layer 24 are formed over theentire display region, formation of the conductive layers in the samestep can reduce display unevenness.

The insulating layer 28 has a function of a dielectric of the capacitor11. In the example shown in FIG. 12A, an inorganic insulating materialis used for the insulating layer 28. When the insulating layer 28 isformed using an inorganic insulating material, the insulating layer 28having a uniform thickness can be formed easily, and furthermore, theinsulating layer 28 can be thinner than the case of using an organicinsulating material. Therefore, variation in the capacitances of thecapacitors 11 can be reduced. Like the insulating layer 264, theinsulating layer 28 can function as an etching stopper at the time ofprocessing the conductive layer 25. Note that the insulating layer 28may be formed using an organic insulating material. In this case, amaterial with low heat resistance can be used for components between thesubstrate 21 and the insulating layer 28, and therefore, the range ofchoices of materials thereof can be expanded.

The conductive layer 25 is provided to cover part of the insulatinglayer 28. The conductive layer 25 is provided to overlap with thelight-blocking layer 53. Part of the conductive layer 25 overlaps withthe conductive layer 23 in a region. The conductive layer 25 has afunction of electrically connecting the two conductive layers 24 betweenwhich the conductive layer 23 is provided, through the openings formedin the insulating layer 28.

The insulating layer 266 is provided to cover the conductive layer 25and the insulating layer 28, and the coloring layer 52 is provided tocover part of the insulating layer 266. The overcoat 267 may be providedto cover the coloring layer 52.

It is preferable that the insulating layer 266 have a function of aplanarization layer and be formed using an organic insulating material.Alternatively, an inorganic insulating material having high planaritymay be used. A flat surface provided by the insulating layer 266 canreduce a variation in the thickness of the coloring layer 52. Thus, thetouch panel can have high display quality.

When a flexible substrate is used for at least one of the substrates 21and 31, the touch panel can be thin and lightweight. When a flexiblesubstrate is used for each of the substrates 21 and 31, the touch panelcan be flexible.

A color filter method is employed in the touch panel shown in FIGS. 12Aand 12B. For example, a structure where pixels of three colors of red(R), green (G), and blue (B) express one color can be employed for thecoloring layer 52. In addition, a pixel of white (W) or yellow (Y) maybe used for the structure.

An EL layer that emits white light is preferably used as the EL layer222 of the light-emitting element 204. By using the light-emittingelement 204, it is not necessary to separately form the EL layers 222expressing different colors in pixels. Therefore, the cost can bereduced, and the high resolution is achieved easily. Furthermore, byvarying the thickness of the optical adjustment layer 224 in pixels,light with a wavelength suitable for each pixel can be extracted, whichincreases color purity. Note that the EL layers 222 expressing differentcolors may be separately formed in pixels, in which case the opticaladjustment layer 224 is not necessarily used.

An opening is provided in the insulating layers and the like in a regionoverlapping with the contact portion 205 provided over the substrate 31,and the contact portion 205 and the FPC 41 are electrically connected toeach other with a connection layer 260 provided in the opening.Furthermore, an opening is provided in the insulating layers and thelike in a region overlapping with the substrate 21, and the contactportion 253 and the FPC 42 are electrically connected to each otherthrough a connection layer 210 provided in the opening.

Note that as shown in FIG. 13 or FIG. 14 , a structure in which the FPC41 and the connection layer 260 do not overlap with the substrate 21 andthe insulating layer and the like provided for the substrate 21 may beemployed. Similarly, in the structures shown in FIG. 13 and FIG. 14 ,the FPC 42 and the connection layer 210 do not overlap with thesubstrate 31 and the insulating layer and the like provided for thesubstrate 31.

In the structure shown in FIG. 12A, the contact portion 205 has aconductive layer formed by processing a conductive film that is alsoused for the source electrode and the drain electrode of the transistor.Furthermore, the contact portion 253 has a stacked-layer structure of aconductive layer formed by processing a conductive film that is alsoused for the conductive layer 23 and the conductive layer 24, and aconductive layer formed by processing a conductive film that is alsoused for the conductive layer 25. The contact portion preferably has astacked-layer structure of a plurality of conductive layers as describedabove because electric resistance can be reduced and mechanical strengthcan be increased.

Furthermore, FIG. 12A shows a cross-sectional structure of a crossingportion 206 where a wiring formed by processing the conductive film usedfor forming the gate electrode of the transistor and a wiring formed byprocessing the conductive film used for forming the source electrode andthe drain electrode of the transistor cross each other.

As the connection layer 210 and the connection layer 260, any of variousanisotropic conductive films (ACF), anisotropic conductive pastes (ACP),or the like can be used.

A material in which impurities such as water or hydrogen do not easilydiffuse is preferably used for the insulating layer 212 and theinsulating layer 262. That is, the insulating layer 212 and theinsulating layer 262 can each function as a barrier film. Such astructure can effectively suppress diffusion of the impurities to thelight-emitting element 204 and the transistors even in the case of usinga material permeable to moisture for the substrate 21 and the substrate31, and a highly reliable touch panel can be achieved.

Here, the distance between one of the conductive layer 23 and theconductive layer 24 (or the conductive layer 25) which is positionedcloser to the display panel (i.e., the substrate side on which thedisplay element is provided) than the other and a conductive layer whichis the closest to the one of the conductive layer 23 and the conductivelayer 24 (or the conductive layer 25) of the conductive layers providedcloser to the display panel than the one of the conductive layer 23 andthe conductive layer 24 (or the conductive layer 25) is preferablygreater than or equal to 25 nm and less than or equal to 100 μm, morepreferably greater than or equal to 50 nm and less than or equal to 10μm, still more preferably greater than or equal to 50 nm and less thanor equal to 5 μm.

In the example shown in FIG. 12A, the second electrode 223 of thelight-emitting element 204 corresponds to the conductive layer which isthe closest to the conductive layer 24 in a region of the pixel 33 ofthe conductive layers provided closer to the display panel than theconductive layer 24. Here, the distance between the conductive layer 24and the second electrode 223 is denoted by D. As the distance D isshorter, a distance between the pair of substrates can be reduced more,and the thickness of the touch panel can be reduced more. In particular,when flexible substrates are used as the pair of substrates, the touchpanel can be flexible and strong against bending.

Note that the conductive layer which is the closest to the conductivelayer 23 or 24 of the conductive layers provided closer to the displaypanel than the conductive layer 23 or 24 is not limited to the secondelectrode 223 and may be a conductive layer other than the secondelectrode 223. For example, in the case where another conductive layeris provided between the second electrode 223 and the conductive layer 23or 24, the distance between the conductive layer and the conductivelayer 23 or 24 is set within the above-described range. For example, aconductive layer can be provided on the insulating layer 266 so that theadhesive layer 220 can be formed on a surface with higher wettability orhigher adhesion.

Components

The above components are described below.

The transistor includes a conductive layer functioning as the gateelectrode, the semiconductor layer, a conductive layer functioning asthe source electrode, a conductive layer functioning as the drainelectrode, and an insulating layer functioning as a gate insulatinglayer. FIG. 12A shows the case where a bottom-gate transistor is used.

Note that there is no particular limitation on the structure of thetransistor included in the touch panel of one embodiment of the presentinvention. For example, a forward staggered transistor or an invertedstaggered transistor may be used. A top-gate transistor or a bottom-gatetransistor may be used. A semiconductor material used for the transistoris not particularly limited, and for example, an oxide semiconductor,silicon, or germanium can be used.

There is no particular limitation on the crystallinity of asemiconductor material used for the transistor, and an amorphoussemiconductor or a semiconductor having crystallinity (amicrocrystalline semiconductor, a polycrystalline semiconductor, asingle-crystal semiconductor, or a semiconductor partly includingcrystal regions) may be used. It is preferable that a semiconductorhaving crystallinity be used, in which case deterioration of thetransistor characteristics can be suppressed.

As a semiconductor material for the semiconductor layer of thetransistor, an element of Group 14, a compound semiconductor, or anoxide semiconductor can be used, for example. Typically, a semiconductorcontaining silicon, a semiconductor containing gallium arsenide, anoxide semiconductor containing indium, or the like can be used.

An oxide semiconductor is preferably used as a semiconductor in which achannel of the transistor is formed. In particular, an oxidesemiconductor having a wider band gap than silicon is preferably used. Asemiconductor material having a wider band gap and a lower carrierdensity than silicon is preferably used because off-state current of thetransistor can be reduced.

For example, the oxide semiconductor preferably contains at least indium(In) or zinc (Zn). The oxide semiconductor more preferably contains anIn—M—Zn-based oxide (M is a metal such as Al, Ti, Ga, Ge, Y, Zr, Sn, La,Ce, or Hf).

As the semiconductor layer, it is particularly preferable to use anoxide semiconductor film including a plurality of crystal parts whosec-axes are aligned substantially perpendicular to a surface on which thesemiconductor layer is formed or the top surface of the semiconductorlayer and having no grain boundary between adjacent crystal parts.

There is no grain boundary in such an oxide semiconductor; thus,generation of a crack in an oxide semiconductor film which is caused bystress when a display panel is bent is prevented. Therefore, such anoxide semiconductor can be preferably used for a flexible touch panelwhich is used in a bent state, or the like.

Moreover, the use of such an oxide semiconductor for the semiconductorlayer makes it possible to provide a highly reliable transistor in whicha change in the electrical characteristics is suppressed.

Charge accumulated in a capacitor through a transistor can be held for along time because of the low off-state current of the transistor. Whensuch a transistor is used for a pixel, operation of a driver circuit canbe stopped while a gray scale of an image displayed in each displayregion is maintained. As a result, a display device with an extremelylow power consumption can be obtained.

Alternatively, silicon is preferably used as a semiconductor in which achannel of a transistor is formed. Although amorphous silicon may beused as silicon, silicon having crystallinity is particularlypreferable. For example, microcrystalline silicon, polycrystallinesilicon, single crystal silicon, or the like is preferably used. Inparticular, polycrystalline silicon can be formed at a lower temperaturethan single crystal silicon and has higher field effect mobility andhigher reliability than amorphous silicon. When such a polycrystallinesemiconductor is used for a pixel, the aperture ratio of the pixel canbe improved. Even in the case where pixels are provided at extremelyhigh resolution, a gate driver circuit and a source driver circuit canbe formed over a substrate over which the pixels are formed, and thenumber of components of an electronic appliance can be reduced.

As conductive layers such as a gate, a source, and a drain of thetransistor and a wiring and an electrode in the touch panel, asingle-layer structure or a stacked-layer structure using any of metalssuch as aluminum, titanium, chromium, nickel, copper, yttrium,zirconium, molybdenum, silver, tantalum, and tungsten, or an alloycontaining any of these metals as its main component can be used. Forexample, a single-layer structure of an aluminum film containingsilicon, a two-layer structure in which an aluminum film is stacked overa titanium film, a two-layer structure in which an aluminum film isstacked over a tungsten film, a two-layer structure in which a copperfilm is stacked over a copper-magnesium-aluminum alloy film, a two-layerstructure in which a copper film is stacked over a titanium film, atwo-layer structure in which a copper film is stacked over a tungstenfilm, a three-layer structure in which a titanium film or a titaniumnitride film, an aluminum film or a copper film, and a titanium film ora titanium nitride film are stacked in this order, a three-layerstructure in which a molybdenum film or a molybdenum nitride film, analuminum film or a copper film, and a molybdenum film or a molybdenumnitride film are stacked in this order, and the like can be given. Notethat a transparent conductive material containing indium oxide, tinoxide, or zinc oxide may be used. Copper containing manganese ispreferably used because controllability of a shape by etching isincreased.

As a light-transmitting conductive material, a conductive oxide such asindium oxide, indium tin oxide, indium zinc oxide, zinc oxide, or zincoxide to which gallium is added, or graphene can be used. Alternatively,a metal material such as gold, silver, platinum, magnesium, nickel,tungsten, chromium, molybdenum, iron, cobalt, copper, palladium, ortitanium, or an alloy material containing any of these metal materialscan be used. Alternatively, a nitride of the metal material (e.g.,titanium nitride) or the like may be used. In the case of using themetal material or the alloy material (or the nitride thereof), thethickness is set small enough to be able to transmit light.Alternatively, a stack of any of the above materials can be used as theconductive layer. For example, a stack of indium tin oxide and an alloyof silver and magnesium is preferably used because the conductivity canbe increased.

Examples of an insulating material that can be used for the insulatinglayers, the overcoat 267, the spacer 219, and the like include a resinsuch as acrylic or epoxy resin, a resin having a siloxane bond, and aninorganic insulating material such as silicon oxide, silicon oxynitride,silicon nitride oxide, silicon nitride, or aluminum oxide.

As described above, the light-emitting element is preferably providedbetween a pair of insulating films with low water permeability. Thus, animpurity such as water can be prevented from entering the light-emittingelement, leading to prevention of a decrease in the reliability of thelight-emitting device.

As an insulating film with low water permeability, a film containingnitrogen and silicon (e.g., a silicon nitride film or a silicon nitrideoxide film), a film containing nitrogen and aluminum (e.g., an aluminumnitride film), or the like can be used. Alternatively, a silicon oxidefilm, a silicon oxynitride film, an aluminum oxide film, or the like canbe used.

For example, the water vapor transmittance of the insulating film withlow water permeability is lower than or equal to 1×10⁻⁵ [g/(m²·day)],preferably lower than or equal to 1×10⁻⁶ [g/(m²·day)], furtherpreferably lower than or equal to 1×10⁻⁷ [g/(m²·day)], still furtherpreferably lower than or equal to 1×10⁻⁸ [g/(m²·day)].

For the adhesive layers, a curable resin such as a heat curable resin, aphotocurable resin, or a two-component type curable resin can be used.For example, a resin such as an acrylic resin, a urethane resin, anepoxy resin, or a resin having a siloxane bond can be used.

The EL layer 222 includes at least a light-emitting layer. In additionto the light-emitting layer, the EL layer 222 may further include one ormore layers containing any of a substance with a high hole-injectionproperty, a substance with a high hole-transport property, ahole-blocking material, a substance with a high electron-transportproperty, a substance with a high electron-injection property, asubstance with a bipolar property (a substance with a high electron- andhole-transport property), and the like.

For the EL layer 222, either a low molecular compound or a highmolecular compound can be used, and an inorganic compound may be used.Each of the layers included in the EL layer 222 can be formed by any ofthe following methods: an evaporation method (including a vacuumevaporation method), a transfer method, a printing method, an inkjetmethod, a coating method, and the like.

In the case where a light-emitting element emitting white light is usedas the light-emitting element 204, the EL layer 222 preferably containstwo or more kinds of light-emitting substances. For example,light-emitting substances are selected so that two or morelight-emitting substances emit complementary colors to obtain whitelight emission. Specifically, it is preferable to contain two or moreselected from light-emitting substances emitting light of red (R), green(G), blue (B), yellow (Y), orange (O), and the like and light-emittingsubstances emitting light containing two or more of spectral componentsof R, G, and B. The light-emitting element 204 preferably emits lightwith a spectrum having two or more peaks in the wavelength range of avisible light region (e.g., 350 nm to 750 nm). An emission spectrum of amaterial emitting light having a peak in the wavelength range of ayellow light preferably includes spectral components also in thewavelength range of a green light and a red light.

More preferably, a light-emitting layer containing a light-emittingmaterial emitting light of one color and a light-emitting layercontaining a light-emitting material emitting light of another color arestacked in the EL layer 222. For example, the plurality oflight-emitting layers in the EL layer 222 may be stacked in contact witheach other or may be stacked with a separation layer therebetween. Forexample, a separation layer may be provided between a fluorescent layerand a phosphorescent layer.

The separation layer can be provided to prevent an energy transfer bythe Dexter mechanism (particularly triplet energy transfer) from aphosphorescent material or the like in an excited state which isgenerated in the phosphorescent layer to a fluorescent material or thelike in the fluorescent layer. The thickness of the separation layer maybe approximately several nanometers, specifically 0.1 nm or more and 20nm or less, 1 nm or more and 10 nm or less, or 1 nm or more and 5 nm orless. The separation layer contains a single material (preferably abipolar material) or a plurality of materials (preferably, ahole-transport material and an electron-transport material).

The separation layer may be formed using a material contained in thelight-emitting layer in contact with the separation layer. Thisfacilitates the manufacture of the light-emitting element and reducesthe drive voltage. For example, in the case where the phosphorescentlayer contains a host material, an assist material, and thephosphorescent material (a guest material), the separation layer maycontain the host material and the assist material. In other words, theseparation layer includes a region which does not contain thephosphorescent material, while the phosphorescent layer includes aregion containing the phosphorescent material. Thus, the separationlayer and the phosphorescent layer can be separately deposited dependingon the presence of the phosphorescent material. Furthermore, such astructure enables the separation layer and the phosphorescent layer tobe deposited in the same chamber, which leads to a reduction inmanufacturing cost.

The light-emitting element 204 may be a single element including one ELlayer or a tandem element in which a plurality of EL layers are stackedwith a charge generation layer therebetween.

Manufacturing Method Example

Here, a method for manufacturing a flexible touch panel is described.

For convenience, a structure including a pixel and a circuit, astructure including an optical member such as a color filter, or astructure including a touch sensor is referred to as an element layer.An element layer includes a display element, for example, and mayinclude a wiring electrically connected to the display element or anelement such as a transistor used in a pixel or a circuit in addition tothe display element.

Here, a support body (e.g., the substrate 21 or the substrate 31) withan insulating surface where an element layer is formed is referred to asa base material.

As a method for forming an element layer over a flexible base materialprovided with an insulating surface, there are a method in which anelement layer is formed directly over a base material, and a method inwhich an element layer is formed over a supporting base material thathas stiffness and then the element layer is separated from thesupporting base material and transferred to the base material.

In the case where a material of the base material can withstand heatingtemperature in a process for forming the element layer, it is preferablethat the element layer be formed directly over the base material, inwhich case a manufacturing process can be simplified. At this time, theelement layer is preferably formed in a state where the base material isfixed to the supporting base material, in which case transfer thereof inan apparatus and between apparatuses can be easy.

In the case of employing the method in which the element layer is formedover the supporting base material and then transferred to the basematerial, first, a separation layer and an insulating layer are stackedover the supporting base material, and then the element layer is formedover the insulating layer. Next, the element layer is separated from thesupporting base material and then transferred to the base material. Atthis time, a material is selected that would cause separation at aninterface between the supporting base material and the separation layer,at an interface between the separation layer and the insulating layer,or in the separation layer.

For example, it is preferable that a stacked layer of a layer includinga high-melting-point metal material, such as tungsten, and a layerincluding an oxide of the metal material be used as the separationlayer, and a stacked layer of a plurality of layers, such as a siliconnitride layer and a silicon oxynitride layer be used over the separationlayer. The use of the high-melting-point metal material is preferablebecause the degree of freedom of the process for forming the elementlayer can be increased.

The separation may be performed by application of mechanical power, byetching of the separation layer, by dripping of a liquid into part ofthe separation interface to penetrate the entire separation interface,or the like. Alternatively, separation may be performed by heating theseparation interface by utilizing a difference in thermal expansioncoefficient.

The separation layer is not necessarily provided in the case whereseparation can occur at an interface between the supporting basematerial and the insulating layer. For example, glass is used as thesupporting base material and an organic resin such as polyimide is usedas the insulating layer, a separation trigger is formed by locallyheating part of the organic resin by laser light or the like, andseparation is performed at an interface between the glass and theinsulating layer.

Alternatively, a metal layer may be provided between the supporting basematerial and the insulating layer formed of an organic resin, andseparation may be performed at the interface between the metal layer andthe insulating layer by heating the metal layer by feeding a current tothe metal layer. In that case, the insulating layer formed of an organicresin can be used as a base material.

Examples of such a base material having flexibility include polyesterresins such as polyethylene terephthalate (PET) and polyethylenenaphthalate (PEN), a polyacrylonitrile resin, a polyimide resin, apolymethyl methacrylate resin, a polycarbonate (PC) resin, apolyethersulfone (PES) resin, a polyamide resin, a cycloolefin resin, apolystyrene resin, a polyamide imide resin, and a polyvinyl chlorideresin. In particular, it is preferable to use a material with a lowthermal expansion coefficient, and for example, a polyamide imide resin,a polyimide resin, PET, or the like with a thermal expansion coefficientlower than or equal to 30×10⁻⁶/K can be suitably used. A substrate inwhich a fibrous body is impregnated with a resin (also referred to asprepreg) or a substrate whose thermal expansion coefficient is reducedby mixing an inorganic filler with an organic resin can also be used.

In the case where a fibrous body is included in the above material, ahigh-strength fiber of an organic compound or an inorganic compound isused as the fibrous body. The high-strength fiber is specifically afiber with a high tensile elastic modulus or a fiber with a high Young'smodulus. Typical examples thereof include a polyvinyl alcohol basedfiber, a polyester based fiber, a polyamide based fiber, a polyethylenebased fiber, an aramid based fiber, a polyparaphenylene benzobisoxazolefiber, a glass fiber, and a carbon fiber. As the glass fiber, glassfiber using E glass, S glass, D glass, Q glass, or the like can be used.These fibers may be used in a state of a woven fabric or a nonwovenfabric, and a structure body in which this fibrous body is impregnatedwith a resin and the resin is cured may be used as the flexiblesubstrate. The structure body including the fibrous body and the resinis preferably used as the flexible substrate, in which case thereliability against bending or breaking due to local pressure can beincreased.

Alternatively, glass, metal, or the like that is thin enough to haveflexibility can be used as the base material. Alternatively, a compositematerial where glass and a resin material are attached to each other maybe used.

In the structure shown in FIG. 12A, for example, a first separationlayer and the insulating layer 262 are formed in this order over a firstsupporting base material, and then components in a layer over the firstseparation layer and the insulating layer 262 are formed. Separately, asecond separation layer and the insulating layer 212 are formed in thisorder over a second supporting base material, and then upper componentsare formed. Next, the first supporting base material and the secondsupporting base material are bonded to each other using the adhesivelayer 220. After that, separation at an interface between the secondseparation layer and the insulating layer 212 is conducted so that thesecond supporting base material and the second separation layer areremoved, and then the substrate 31 is bonded to the insulating layer 212using the adhesive layer 211. Further, separation at an interfacebetween the first separation layer and the insulating layer 262 isconducted so that the first supporting base material and the firstseparation layer are removed, and then the substrate 21 is bonded to theinsulating layer 262 using the adhesive layer 261. Note that either sidemay be subjected to separation and attachment first.

The above is the description of a manufacturing method of a flexibletouch panel.

Cross-Sectional Structure Example 2

FIG. 15 is a cross-sectional structure example whose structure is partlydifferent from that of FIG. 12A. Note that descriptions of the portionsalready described are omitted and different portions are describedbelow.

In the example shown in FIG. 15 , the conductive layer 25 is notprovided. The conductive layer 24 is provided to cover part of theinsulating layer 28. The conductive layer 23 and the conductive layer 24overlap with each other in a region, and the capacitor 11 is formed inthe region.

FIG. 15 also shows a cross-sectional structure of a connection portion272 in which the conductive layer 24 is electrically connected to awiring formed by processing the conductive film used for forming theconductive layer 23 through an opening formed in the insulating layer28.

In the example shown in FIG. 15 , the EL layer 222 is separately formedin each pixel. The EL layer 222 can include a light-emitting layercontaining a light-emitting material emitting light of one color. In thelight-emitting element 204 shown in FIG. 15 , the optical adjustmentlayer 224 shown in FIG. 12B is not included. Furthermore, the coloringlayer 52 is not provided in FIG. 15 . In this manner, the structure ofthe light-emitting element can be simplified in the case where the ELlayer 222 of the light-emitting element 204 is separately formed in eachpixel to obtain light emission with high color purity from thelight-emitting element 204.

Here, the distance between one of the conductive layer 23 and theconductive layer 24 which is positioned closer to the display panel thanthe other and a conductive layer which is the closest to the one of theconductive layers 23 and 24 of the conductive layers provided closer tothe display panel than the one of the conductive layers 23 and 24 ispreferably greater than or equal to 25 nm and less than or equal to 100μm, more preferably greater than or equal to 50 nm and less than orequal to 10 μm, still more preferably greater than or equal to 50 nm andless than or equal to 5 μm.

In the example shown in FIG. 15 , the second electrode 223 of thelight-emitting element 204 corresponds to the conductive layer which isthe closest to the conductive layer 24 of the conductive layers providedcloser to the display panel than the conductive layer 24. Here, as thedistance D between the conductive layer 24 and the second electrode 223is shorter, a distance between the pair of substrates can be reducedmore, and the thickness of the touch panel can be reduced more. Inparticular, when a flexible substrate is used as the pair of substrates,the touch panel can be flexible and strong against bending.

The above is the description of the cross-sectional structure example 2.

Though this embodiment shows the structure including two substrates,i.e., the substrate supporting the touch sensor and the substratesupporting the display element, the structure is not limited thereto.For example, a structure with three substrates where a display elementis sandwiched between two substrates and the substrate supporting atouch sensor is bonded thereto can be employed. Alternatively, astructure with four substrates where a display element sandwichedbetween two substrates and a touch sensor sandwiched between twosubstrates are bonded to each other can be employed.

This embodiment can be combined with any of the other embodimentsdisclosed in this specification as appropriate.

Embodiment 2

In this embodiment, an example of a method for operating the touch panelof one embodiment of the present invention is described with referenceto drawings.

Example of Sensing Method of Sensor

FIG. 16A is a block diagram illustrating the structure of a mutualcapacitive touch sensor. FIG. 16A illustrates a pulse voltage outputcircuit 601 and a current sensing circuit 602. Note that in FIG. 16A,six wirings X1 to X6 represent the electrodes 621 to which a pulsevoltage is applied, and six wirings Y1 to Y6 represent the electrodes622 that detect changes in current. FIG. 16A also illustrates acapacitor 603 that is formed where the electrodes 621 and 622 overlapwith each other. Note that functional replacement between the electrodes621 and 622 is possible.

The pulse voltage output circuit 601 is a circuit for sequentiallyapplying a pulse voltage to the wirings X1 to X6. By application of apulse voltage to the wirings X1 to X6, an electric field is generatedbetween the electrodes 621 and 622 of the capacitor 603. When theelectric field between the electrodes is shielded, for example, a changeoccurs in the capacitor 603 (mutual capacitance). The approach orcontact of a sensing target can be sensed by utilizing this change.

The current sensing circuit 602 is a circuit for detecting changes incurrent flowing through the wirings Y1 to Y6 that are caused by thechange in mutual capacitance in the capacitor 603. No change in currentvalue is detected in the wirings Y1 to Y6 when there is no approach orcontact of a sensing target, whereas a decrease in current value isdetected when mutual capacitance is decreased owing to the approach orcontact of a sensing target. Note that an integrator circuit or the likeis used for sensing of current values.

FIG. 16B is a timing chart showing input and output waveforms in themutual capacitive touch sensor illustrated in FIG. 16A. In FIG. 16B,sensing of a sensing target is performed in all the rows and columns inone frame period. FIG. 16B shows a period when a sensing target is notsensed (not touched) and a period when a sensing target is sensed(touched). Sensed current values of the wirings Y1 to Y6 are shown asthe waveforms of voltage values.

A pulse voltage is sequentially applied to the wirings X1 to X6, and thewaveforms of the wirings Y1 to Y6 change in accordance with the pulsevoltage. When there is no approach or contact of a sensing target, thewaveforms of the wirings Y1 to Y6 change in accordance with changes inthe voltages of the wirings X1 to X6. The current value is decreased atthe point of approach or contact of a sensing target and accordingly thewaveform of the voltage value changes.

By detecting a change in mutual capacitance in this manner, the approachor contact of a sensing target can be sensed.

It is preferable that the pulse voltage output circuit 601 and thecurrent sensing circuit 602 be mounted on a substrate in a housing of anelectronic appliance or on the touch panel in the form of an IC. In thecase where the touch panel has flexibility, parasitic capacitance mightbe increased in a bent portion of the touch panel, and the influence ofnoise might be increased. In view of this, it is preferable to use an ICto which a driving method less influenced by noise is applied. Forexample, it is preferable to use an IC to which a driving method capableof increasing a signal-noise ratio (S/N ratio) is applied.

Although FIG. 16A is a passive matrix type touch sensor in which onlythe capacitor 603 is provided at the intersection of wirings as a touchsensor, an active matrix type touch sensor including a transistor and acapacitor may be used. FIG. 17 is a sensor circuit included in an activematrix type touch sensor.

The sensor circuit includes the capacitor 603 and transistors 611, 612,and 613. A signal G2 is input to a gate of the transistor 613. A voltageVRES is applied to one of a source and a drain of the transistor 613,and one electrode of the capacitor 603 and a gate of the transistor 611are electrically connected to the other of the source and the drain ofthe transistor 613. One of a source and a drain of the transistor 611 iselectrically connected to one of a source and a drain of the transistor612, and a voltage VSS is applied to the other of the source and thedrain of the transistor 611. A signal G1 is input to a gate of thetransistor 612, and a wiring ML is electrically connected to the otherof the source and the drain of the transistor 612. The voltage VSS isapplied to the other electrode of the capacitor 603.

Next, the operation of the sensor circuit will be described. First, apotential for turning on the transistor 613 is supplied as the signalG2, and a potential with respect to the voltage VRES is thus applied tothe node n connected to the gate of the transistor 611. Then, apotential for turning off the transistor 613 is applied as the signalG2, whereby the potential of the node n is maintained.

Then, mutual capacitance of the capacitor 603 changes owing to theapproach or contact of a sensing target such as a finger, andaccordingly the potential of the node n is changed from VRES.

In reading operation, a potential for turning on the transistor 612 issupplied as the signal G1. A current flowing through the transistor 611,that is, a current flowing through the wiring ML is changed inaccordance with the potential of the node n. By sensing this current,the approach or contact of a sensing target can be sensed.

It is preferred that the transistors 611, 612, and 613 each include anoxide semiconductor in a semiconductor layer where a channel is formed.In particular, by using an oxide semiconductor in a semiconductor layerwhere a channel of the transistor 613 is formed, the potential of thenode n can be held for a long time and the frequency of operation(refresh operation) of resupplying VRES to the node n can be reduced.

At least part of this embodiment can be implemented in combination withany of the embodiments described in this specification as appropriate.

Embodiment 3

In this embodiment, electronic appliances and lighting devices that canbe fabricated according to one embodiment of the present invention willbe described with reference to FIGS. 18A to 18G and FIGS. 19A to 19I.

The touch panel of one embodiment of the present invention hasflexibility. Therefore, a touch panel of one embodiment of the presentinvention can be used in electronic appliances and lighting deviceshaving flexibility. Furthermore, according to one embodiment of thepresent invention, electronic appliances and lighting devices havinghigh reliability and resistance against repeated bending can bemanufactured.

Examples of electronic appliances include a television set (alsoreferred to as a television or a television receiver), a monitor of acomputer or the like, a digital camera, a digital video camera, adigital photo frame, a mobile phone (also referred to as a mobile phonedevice), a portable game machine, a portable information terminal, anaudio reproducing device, a large game machine such as a pinballmachine, and the like.

The touch panel of one embodiment of the present invention hasflexibility and therefore can be incorporated along a curvedinside/outside wall surface of a house or a building or a curvedinterior/exterior surface of a car.

An electronic appliance of one embodiment of the present invention mayinclude a touch panel and a secondary battery. It is preferable that thesecondary battery is capable of being charged by contactless powertransmission.

As examples of the secondary battery, a lithium ion secondary batterysuch as a lithium polymer battery (lithium ion polymer battery) using agel electrolyte, a lithium ion battery, a nickel-hydride battery, anickel-cadmium battery, an organic radical battery, a lead-acid battery,an air secondary battery, a nickel-zinc battery, and a silver-zincbattery can be given.

The electronic appliance of one embodiment of the present invention mayinclude a touch panel and an antenna. When a signal is received by theantenna, the electronic appliance can display an image, data, or thelike on a display portion. When the electronic appliance includes asecondary battery, the antenna may be used for contactless powertransmission.

FIG. 18A illustrates an example of a mobile phone. The mobile phone 7400is provided with a display portion 7402 incorporated in a housing 7401,operation buttons 7403, an external connection port 7404, a speaker7405, a microphone 7406, and the like. Note that the mobile phone 7400is manufactured by using the touch panel of one embodiment of thepresent invention for the display portion 7402. In accordance with oneembodiment of the present invention, a highly reliable mobile phonehaving a curved display portion can be provided at a high yield.

When the display portion 7402 of the mobile phone 7400 illustrated inFIG. 18A is touched with a finger or the like, data can be input intothe mobile phone 7400. Further, operations such as making a call andinputting a letter can be performed by touch on the display portion 7402with a finger or the like.

With the operation buttons 7403, power ON or OFF can be switched. Inaddition, types of images displayed on the display portion 7402 can beswitched; switching images from a mail creation screen to a main menuscreen.

FIG. 18B illustrates an example of a wrist-watch-type portableinformation terminal. A portable information terminal 7100 includes ahousing 7101, a display portion 7102, a band 7103, a buckle 7104, anoperation button 7105, an input/output terminal 7106, and the like.

The portable information terminal 7100 is capable of executing a varietyof applications such as mobile phone calls, e-mailing, reading andediting texts, music reproduction, Internet communication, and acomputer game.

The display surface of the display portion 7102 is bent, and images canbe displayed on the bent display surface. Furthermore, the displayportion 7102 includes a touch sensor, and operation can be performed bytouching the screen with a finger, a stylus, or the like. For example,by touching an icon 7107 displayed on the display portion 7102, anapplication can be started.

With the operation button 7105, a variety of functions such as timesetting, power ON/OFF, ON/OFF of wireless communication, setting andcancellation of manner mode, and setting and cancellation of powersaving mode can be performed. For example, the functions of theoperation button 7105 can be set freely by setting the operating systemincorporated in the portable information terminal 7100.

The portable information terminal 7100 can employ near fieldcommunication that is a communication method based on an existingcommunication standard. In that case, for example, mutual communicationbetween the portable information terminal 7100 and a headset capable ofwireless communication can be performed, and thus hands-free calling ispossible.

Moreover, the portable information terminal 7100 includes theinput/output terminal 7106, and data can be directly transmitted to andreceived from another information terminal via a connector. Chargingthrough the input/output terminal 7106 is possible. Note that thecharging operation may be performed by wireless power feeding withoutusing the input/output terminal 7106.

The display portion 7102 of the portable information terminal 7100includes the touch panel of one embodiment of the present invention.According to one embodiment of the present invention, a highly reliableportable information terminal having a curved display portion can beprovided with a high yield.

FIGS. 18C to 18E illustrate examples of a lighting device. Lightingdevices 7200, 7210, and 7220 each include a stage 7201 provided with anoperation switch 7203 and a light-emitting portion supported by thestage 7201.

The lighting device 7200 illustrated in FIG. 18C includes alight-emitting portion 7202 having a wave-shaped light-emitting surface,and thus has good design.

A light-emitting portion 7212 included in the lighting device 7210illustrated in FIG. 18D has two convex-curved light-emitting portionssymmetrically placed. Thus, all directions can be illuminated with thelighting device 7210 as a center.

The lighting device 7220 illustrated in FIG. 18E includes aconcave-curved light-emitting portion 7222. This is suitable forilluminating a specific range because light emitted from theconcave-curved light-emitting portion 7222 is collected to the front ofthe lighting device 7220.

The light-emitting portion included in each of the lighting devices7200, 7210, and 7220 is flexible; thus, the light-emitting portion maybe fixed on a plastic member, a movable frame, or the like so that anemission surface of the light-emitting portion can be bent freelydepending on the intended use.

Note that although the lighting device in which the light-emittingportion is supported by the stage is described as an example here, ahousing provided with a light-emitting portion can be fixed on a ceilingor suspended from a ceiling. Since the light-emitting surface can becurved, the light-emitting surface is curved to have a depressed shape,whereby a particular region can be brightly illuminated, or thelight-emitting surface is curved to have a projecting shape, whereby awhole room can be brightly illuminated.

Here, the light-emitting portions each include the touch panel of oneembodiment of the present invention. In accordance with one embodimentof the present invention, a highly reliable lighting device having acurved light-emitting portion can be provided at a high yield.

FIG. 18F illustrates an example of a portable touch panel. A touch panel7300 includes a housing 7301, a display portion 7302, operation buttons7303, a display portion pull 7304, and a control portion 7305.

The touch panel 7300 includes a rolled flexible display portion 7302 inthe cylindrical housing 7301.

The touch panel 7300 can receive a video signal with the control portion7305 and can display the received video on the display portion 7302. Inaddition, a battery is included in the control portion 7305. Moreover, aterminal portion for connecting a connector may be included in thecontrol portion 7305 so that a video signal or power can be directlysupplied from the outside with a wiring.

By pressing the operation buttons 7303, power ON/OFF, switching ofdisplayed videos, and the like can be performed.

FIG. 18G illustrates the touch panel 7300 in a state where the displayportion 7302 is pulled out with the display portion pull 7304. Videoscan be displayed on the display portion 7302 in this state. Further, theoperation buttons 7303 on the surface of the housing 7301 allowone-handed operation. The operation buttons 7303 are provided not in thecenter of the housing 7301 but on one side of the housing 7301 asillustrated in FIG. 18F, which makes one-handed operation easy.

Note that a reinforcement frame may be provided for a side portion ofthe display portion 7302 so that the display portion 7302 has a flatdisplay surface when pulled out.

Note that in addition to this structure, a speaker may be provided forthe housing so that sound is output with an audio signal receivedtogether with a video signal.

The display portion 7302 includes the touch panel of one embodiment ofthe present invention. According to one embodiment of the presentinvention, a lightweight and highly reliable touch panel can be providedwith a high yield.

FIGS. 19A to 19C illustrate a foldable portable information terminal310. FIG. 19A illustrates the portable information terminal 310 that isopened. FIG. 19B illustrates the portable information terminal 310 thatis being opened or being folded. FIG. 19C illustrates the portableinformation terminal 310 that is folded. The portable informationterminal 310 is highly portable when folded. When the portableinformation terminal 310 is opened, a seamless large display region ishighly browsable.

A display panel 316 is supported by three housings 315 joined togetherby hinges 313. By folding the portable information terminal 310 at aconnection portion between two housings 315 with the hinges 313, theportable information terminal 310 can be reversibly changed in shapefrom an opened state to a folded state. The touch panel according to oneembodiment of the present invention can be used for the display panel316. For example, a touch panel that can be bent with a radius ofcurvature of greater than or equal to 1 mm and less than or equal to 150mm can be used.

Note that in one embodiment of the present invention, a sensor thatsenses whether the touch panel is in a folded state or an unfolded stateand supplies sensing data may be used. The operation of a folded portion(or a portion that becomes invisible by a user by folding) of the touchpanel may be stopped by a control device through the acquisition of dataindicating the folded state of the touch panel. Specifically, display ofthe portion may be stopped, and furthermore, sensing by the touch sensormay be stopped.

Similarly, the control device of the touch panel may acquire dataindicating the unfolded state of the touch panel to resume displayingand sensing by the touch sensor.

FIGS. 19D and 19E each illustrate a foldable portable informationterminal 320. FIG. 19D illustrates the portable information terminal 320that is folded so that a display portion 322 is on the outside. FIG. 19Eillustrates the portable information terminal 320 that is folded so thatthe display portion 322 is on the inside. When the portable informationterminal 320 is not used, the portable information terminal 320 isfolded so that a non-display portion 325 faces the outside, whereby thedisplay portion 322 can be prevented from being contaminated or damaged.The touch panel in one embodiment of the present invention can be usedfor the display portion 322.

FIG. 19F is a perspective view illustrating an external shape of aportable information terminal 330. FIG. 19G is a top view of theportable information terminal 330. FIG. 19H is a perspective viewillustrating an external shape of a portable information terminal 340.

The portable information terminals 330 and 340 each function as, forexample, one or more of a telephone set, a notebook, and an informationbrowsing system. Specifically, the portable information terminals 330and 340 each can be used as a smartphone.

The portable information terminals 330 and 340 can display charactersand image information on its plurality of surfaces. For example, threeoperation buttons 339 can be displayed on one surface (FIGS. 19F and19H). In addition, information 337 indicated by dashed rectangles can bedisplayed on another surface (FIGS. 19F, 19G, and 19H). Examples of theinformation 337 include notification from a social networking service(SNS), display indicating reception of an e-mail or an incoming call,the title of an e-mail or the like, the sender of an e-mail or the like,the date, the time, remaining battery, and the reception strength of anantenna. Alternatively, the operation buttons 339, an icon, or the likemay be displayed in place of the information 337. Although FIGS. 19F and19G illustrate an example in which the information 337 is displayed atthe top, one embodiment of the present invention is not limited thereto.The information may be displayed, for example, on the side as in theportable information terminal 340 illustrated in FIG. 19H.

For example, a user of the portable information terminal 330 can see thedisplay (here, the information 337) with the portable informationterminal 330 put in a breast pocket of his/her clothes.

Specifically, a caller's phone number, name, or the like of an incomingcall is displayed in a position that can be seen from above the portableinformation terminal 330. Thus, the user can see the display withouttaking out the portable information terminal 330 from the pocket anddecide whether to answer the call.

A touch panel of one embodiment of the present invention can be used fora display portion 333 mounted in each of a housing 335 of the portableinformation terminal 330 and a housing 336 of the portable informationterminal 340. According to one embodiment of the present invention, ahighly reliable touch panel having a curved display portion can beprovided with a high yield.

As in a portable information terminal 345 illustrated in FIG. 19I, datamay be displayed on three or more surfaces. Here, data 355, data 356,and data 357 are displayed on different surfaces.

The touch panel of one embodiment of the present invention can be usedfor a display portion 358 included in a housing 354 of the portableinformation terminal 345. According to one embodiment of the presentinvention, a highly reliable touch panel having a curved display portioncan be provided with a high yield.

At least part of this embodiment can be implemented in combination withany of the embodiments described in this specification as appropriate.

Example

In this example, a foldable touch panel of one embodiment of the presentinvention was fabricated. This example also describes the results ofperforming evaluation of a time constant and performing a folding teston the touch panel.

Fabrication of Touch Panel

In this example, an in-cell touch panel in which a touch sensor wasformed in a counter substrate (a substrate on the display surface side)of a flexible display panel was fabricated. An electrode of the touchsensor had a metal-mesh structure to reduce the load capacitance formedbetween the touch sensor and the display panel. Thus, the whole touchpanel can be thin enough to be freely folded by a user. In addition,because of the small load capacitance, the influence of noise from thedisplay panel to the touch sensor can be suppressed, so that defectssuch as false detection and detection failure can be suppressed.

As a method for driving the in-cell touch panel fabricated in thisexample, a projected mutual capacitive type was employed.

The touch panel having the cross-sectional structure shown in FIGS. 12Aand 12B was fabricated in this example. As the mesh pattern of the touchsensor, the pattern shown in FIG. 6 was used.

FIG. 20 shows a structure of the touch panel fabricated in this example.A schematic view of the touch panel is shown in the center of FIG. 20 ,a cross-sectional structure of the touch panel is shown in the left sidethereof, and an enlarged view of a bent portion of the touch panel isshown in the right side thereof. The touch panel includes a displayportion (denoted by Display) having flexibility and an FPC. In thestructure of the touch panel, two flexible substrates were bonded toeach other with an adhesive layer, and a passivation layer was providedon each of the facing surfaces of the flexible substrates. An FET layer(denoted by FET) and an organic EL element (denoted by OLED) were formedover the passivation layer over one of the flexible substrates. A touchsensor and a color filter were formed over the passivation layer overthe other of the flexible substrates. As shown in FIG. 20 , the touchpanel fabricated in this example can be folded so that its displaysurface has a convex curve and a concave curve.

First, a separation layer, the passivation layer, the FET layer, and theorganic EL element were formed over a glass substrate.

As a transistor (e.g., the transistor 201) included in the FET layer, atransistor including an oxide semiconductor as a semiconductor where achannel is formed was used. Here, a crystalline oxide semiconductorhaving c-axis alignment in a direction perpendicular to a film surface(CAAC-OS: c-axis aligned crystalline-oxide semiconductor) was used asthe oxide semiconductor in this example.

A CAAC-OS is a crystalline oxide semiconductor having c-axis alignmentof crystals in a direction substantially perpendicular to the filmsurface. It has been found that oxide semiconductors have a variety ofcrystal structures other than a single-crystal structure. An example ofsuch structures is a nano-crystal (nc) structure, which is an aggregateof nanoscale microcrystals. The crystallinity of a CAAC-OS structure islower than that of a single-crystal structure and higher than that of annc structure. Moreover, since the CAAC-OS does not have a grainboundary, a stable and uniform film can be formed over a large area, andstress that is caused by bending a flexible light-emitting device doesnot easily make a crack in a CAAC-OS film.

In—Ga—Zn-based oxide was used as the oxide semiconductor material inthis example.

As a pixel electrode (the first electrode 221), alloy containing silverwith extremely high reflectivity was used. A transparent electrode layer(the optical adjustment layer 224) was formed over the pixel electrodeand the thickness thereof varied as appropriate depending on thestructure of the sub-pixel to produce a microcavity effect.

As the organic EL element, a top-emission white EL element was used. Theorganic EL element had a tandem structure in which a blue light-emittingunit and a yellow light-emitting unit were stacked.

Furthermore, a separation layer, the passivation layer, a light-blockinglayer, a touch sensor electrode, and the color filter were formed overanother glass substrate. In order to suppress reflection of light by thetouch sensor electrode, the light-blocking layer was provided betweenthe touch sensor electrode and the passivation layer.

Then, the two substrates were bonded to each other with the adhesivelayer. The distance (cell gap) between the substrates was set toapproximately 5 μm. Then, separation of each substrate was made to occurbetween the separation layer and the passivation layer, and the flexiblesubstrates were attached. The flexible substrates were plasticsubstrates each having a thickness of approximately 20 μm.

In this manner, the touch panel was fabricated. Table 1 shows thespecifications of a display device, and Table 2 shows the specificationsof the touch sensor.

TABLE 1 Specifications of 8.67 inch OLED Display Screen diagonal 8.67inch Driving method Active Matrix Number of effective pixels 1080 × RGBY× 1920 Pixel pitch 0.100 mm × 0.100 mm Pixel density 254 ppi Apertureratio 0.46% Pixel arrangement RGBY checker Pixel circuit 6Tr + 1 C/cellSource driver COF Scan driver Integrated

TABLE 2 Specifications of 8.67 inch Touch Sensor Screen diagonal 8.67inch Driving method Projection capacitance (Mutual capacitance) Sensorstructure Metal mesh Number of sensor units 48(T) × 27(R) Sensor unitpitch 4.00 mm × 4.00 mm

The pixel included in the touch panel fabricated in this exampleincluded four RGBY sub-pixels. The use of the Y (yellow) sub-pixelincreased current efficiency and reduced chromaticity variationdepending on the viewing angle more than the case of using a whitesub-pixel.

For the touch sensor, 48 transmitting electrodes were arranged in thelongitudinal direction of the display portion and 27 receivingelectrodes were arranged in the lateral direction thereof with 4 mmpitches. A matrix of 40×40 pixels in the display portion corresponds toone unit of the touch sensor.

Touch Panel

FIGS. 21A to 21C are photographs of the fabricated touch panel. FIG. 21Ashows a state where the display panel is unfolded. FIG. 21B shows astate where the display panel is folded in three. FIG. 21C shows a statewhere the display panel is touched while folded. It was demonstratedthat a touch on each of a flat surface portion, a convex curved portion,and a concave curved portion of the surface of the touch panel wasdetected appropriately.

Since the pixels are arranged in the openings in the mesh of the touchsensor electrode, providing the touch sensor does not significantlyaffect the light extraction efficiency.

Evaluation of Time Constant

Next, the parasitic capacitance and resistance between the receivingelectrode of the fabricated touch panel and the display panel weremeasured with varying frequency. An LCR meter (4275A manufactured byAgilent Technologies, Inc.) was used for the measurement.

FIG. 22 shows the measurement results. The vertical axis on the leftside, the vertical axis on the right side, and the horizontal axis inFIG. 22 represent parasitic capacitance, parasitic resistance, andfrequency, respectively. The number of measurements was six. As shown inFIG. 22 , with 10 kHz measurement frequency, the parasitic capacitancewas approximately 910 pF, and the parasitic resistance was approximately1.3 kΩ. The time constant was calculated to be approximately 1.2 μs.This value is small but not so small as to cause failure of touchdetection.

Folding Test

Next, the results of performing a folding test on the fabricated touchpanel are described. In the folding test, an operation of folding andunfolding the touch panel with a curvature radius of 5 mm or 3 mm wasperformed once every two seconds, and the operation was repeated 100,000times. The folding and unfolding operation was performed under twodifferent conditions: inward folding (the display surface faces inward)and outward folding (the display surface faces outward). Even after thefolding and unfolding operation was performed 100,000 times, normaldisplay and touch detection were achieved.

These results show that the touch panel of one embodiment of the presentinvention is a foldable touch panel with high reliability, highvisibility, and low power consumption. This touch panel will lead to anovel mobile device.

This application is based on Japanese Patent Application serial no.2014-112316 filed with Japan Patent Office on May 30, 2014, JapanesePatent Application serial no. 2014-128409 filed with Japan Patent Officeon Jun. 23, 2014, and Japanese Patent Application serial no. 2014-242912filed with Japan Patent Office on Dec. 1, 2014, the entire contents ofwhich are hereby incorporated by reference.

What is claimed is:
 1. A touch panel comprising: a first conductivelayer; a second conductive layer; a third conductive layer; a fourthconductive layer; a fifth conductive layer; and an insulating layer,wherein the first conductive layer, the second conductive layer, thethird conductive layer, and the fourth conductive layer are providedover a same plane, wherein the fourth conductive layer is electricallyinsulated from the first conductive layer, the second conductive layer,and the third conductive layer, wherein the fifth conductive layer iselectrically connected to the second conductive layer and the thirdconductive layer, wherein the first conductive layer extends in a firstdirection and the fifth conductive layer extends in a second directionthat crosses the first direction, wherein the first conductive layercomprises a first region which overlaps with the fifth conductive layerwith the insulating layer interposed therebetween and a second regionwhich does not overlap with the fifth conductive layer or the insulatinglayer, wherein the first region is narrower than the second region,wherein the first conductive layer and the fifth conductive layer form acapacitor, wherein the fourth conductive layer has a cross-like shape,and wherein a width of the cross-like shape of the fourth conductivelayer is smaller than a width of the fifth conductive layer.
 2. Thetouch panel according to claim 1, wherein the first conductive layercomprises a first opening, and wherein the second conductive layercomprises a second opening.
 3. The touch panel according to claim 1,further comprising a light-blocking layer over and overlapping with thefirst conductive layer and the second conductive layer.
 4. The touchpanel according to claim 1, wherein a plurality of cross-like patternsare provided as the fourth conductive layer, and wherein each of thecross-like patterns are provided between the first conductive layer andthe second conductive layer or between the first conductive layer andthe second conductive layer.
 5. A module comprising: the touch panelaccording to claim 1; and at least one of a flexible printed circuit anda tape carrier package.
 6. An electronic appliance comprising: the touchpanel according to claim 1; and at least one of a battery, an antenna, ahousing, an operation button, an external connection port, a speaker,and a microphone.
 7. A display device comprising: a first substrate; atransistor over the first substrate; a display element electricallyconnected to the transistor; a first conductive layer; a secondconductive layer; a third conductive layer; a fourth conductive layer; afifth conductive layer; and an insulating layer, wherein the firstconductive layer, the second conductive layer, the third conductivelayer, and the fourth conductive layer are provided over a same plane,wherein the fourth conductive layer is electrically insulated from thefirst conductive layer, the second conductive layer, and the thirdconductive layer, wherein the fifth conductive layer is electricallyconnected to the second conductive layer and the third conductive layer,wherein the first conductive layer extends in a first direction and thefifth conductive layer extends in a second direction that crosses thefirst direction, wherein the first conductive layer comprises a firstregion which overlaps with the fifth conductive layer with theinsulating layer interposed therebetween and a second region which doesnot overlap with the fifth conductive layer or the insulating layer,wherein the first region is narrower than the second region, wherein thefirst conductive layer and the fifth conductive layer form a capacitor,wherein the fourth conductive layer has a cross-like shape, and whereina width of the cross-like shape of the fourth conductive layer issmaller than a width of the fifth conductive layer.
 8. The displaydevice according to claim 7, wherein the first conductive layercomprises a first opening, and wherein the second conductive layercomprises a second opening.
 9. The display device according to claim 7,further comprising a light-blocking layer over and overlapping with thefirst conductive layer and the second conductive layer, wherein a secondsubstrate is over the light-blocking layer.
 10. The display deviceaccording to claim 7, wherein a plurality of cross-like patterns areprovided as the fourth conductive layer, and wherein each of thecross-like patterns are provided between the first conductive layer andthe second conductive layer or between the first conductive layer andthe third conductive layer.
 11. A module comprising: the display deviceaccording to claim 7; and at least one of a flexible printed circuit anda tape carrier package.
 12. An electronic appliance comprising: thedisplay device according to claim 7; and at least one of a battery, anantenna, a housing, an operation button, an external connection port, aspeaker, and a microphone.